: Management of manganese deficiency in fodder crops through mobilization of manganese in rhizosphere
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Date
2008
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Punjab Agricultural University, Ludhiana
Abstract
To study the possibility of managing Mn deficiency in fodder crops through mobilization of Mn in the rhizosphere, berseem, oats, ryegrass and raya were grown in mixed cropping in a Mn-deficient loamy sand soil in two experiments conducted in screen house. Six cropping combinations were examined: berseem monoculture, berseem grown in mixed cropping with oats, ryegrass, raya, raya + oats and raya + ryegrass. Two sets of treatments were maintained; to one set, three foliar sprays of 0.5% MnSO4 solution were applied at weekly intervals after first cutting. In no-Mn treatment (no foliar sprays), root length (RL) and shoot dry weight (SDW) of berseem grown as monoculture was severely inhibited as compared to berseem grown in mixed cropping. In no-Mn berseem monoculture treatment, SDW and RL were, respectively, 71% and 68% of the maximum recorded at 60 days of growth after applying Mn. Corresponding values of SDW and RL of berseem when grown in mixed cropping with raya and ryegrass were 96 and 88% and 88 and 87%, respectively. Application of Mn significantly increased both SDW and RL. There was 1.7 and 1.3 times increase in root length of berseem grown in mixed cropping with ryegrass and raya, respectively as compared to berseem grown as monoculture. Mixed cropping with spray application of Mn resulted in maximum Mn uptake in berseem grown with ryegrass as well as with raya due to well developed root system with larger root surface area. High relative root growth rate and low relative shoot growth rate resulted in high Mn concentration in berseem grown with ryegrass and raya in mixed cropping. Infact, 3 times higher Mn influx in berseem grown with ryegrass or with raya as compared to berseem alone may be the reason of higher Mn content in the shoots. The high Mn influx resulted from high concentration gradient due to depletion of Mn at the root surface to a lower value in berseem grown under similar conditions. DTPA-extractable Mn increased from initial value of 2.72 to 2.76 and 2.78 mg kg-1 soil where berseem was grown in mixed cropping with ryegrass and raya, respectively after harvest of all the crops. This study suggests that mixed cropping of berseem with raya or ryegrass leads to sufficient mobilization of Mn in soil to counteract Mn deficiency.